1. Field of the Invention
This invention pertains to an implant for passing blood flow directly between a chamber of the heart and a coronary vessel. More particularly, this invention pertains to a transmyocardial implant with a coronary vessel inserted into the implant.
2. Description of the Prior Art
Commonly assigned and co-pending U.S. patent application Ser. No. 08/882,397 having related PCT Application No. PCT/US97/13980, entitled "Method and Apparatus for Performing Coronary Bypass Surgery", and filed on Jun. 25, 1997 in the name of inventors Mark B. Knudson and William L. Giese, teaches an implant for defining a blood flow conduit directly from a chamber of the heart to a lumen of a coronary vessel. An embodiment disclosed in the aforementioned application teaches an L-shaped implant in the form of a rigid conduit. The conduit has one leg sized to be received within a lumen of a coronary artery and a second leg sized to pass through the myocardium and extend into the left ventricle of the heart. As disclosed in the above-referenced application, the conduit is rigid and remains open for blood flow to pass through the conduit during both systole and diastole. The conduit penetrates into the left ventricle in order to prevent tissue growth and occlusions over an opening of the conduit.
Commonly assigned and co-pending U.S. patent application Ser. No. 09/009,400 filed Jan. 20, 1998, entitled "Flexible Transmyocardial Implant", and filed in the name of inventor Katherine S. Tweden teaches a transmyocardial implant. The implant includes a rigid conduit placed in the myocardium and which has a vessel graft extending from the conduit to a coronary vessel.
Implants such as those shown in the aforementioned '397 application include a portion to be placed within a coronary vessel and a portion to be placed within the myocardium. When placing the implant in a coronary vessel such as a coronary artery, the vessel may be stretched to fit over the implant. Too much stretching of the artery may result in arterial damage. The risk of excessive stretching is most likely when placing an implant into a small diameter vessel (e.g., 1-2 mm). As the diameter of the implant decreases to accommodate smaller vessels, the ratio of the wall thickness of the implant to the diameter increases. Therefore, the proportional amount of stretching increases with smaller implants. The amount of stretching can be reduced by decreasing the wall thickness of the implant.